xref: /openbmc/linux/arch/um/kernel/process.c (revision 976c46e6)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
4  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
5  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
6  * Copyright 2003 PathScale, Inc.
7  */
8 
9 #include <linux/stddef.h>
10 #include <linux/err.h>
11 #include <linux/hardirq.h>
12 #include <linux/mm.h>
13 #include <linux/module.h>
14 #include <linux/personality.h>
15 #include <linux/proc_fs.h>
16 #include <linux/ptrace.h>
17 #include <linux/random.h>
18 #include <linux/slab.h>
19 #include <linux/sched.h>
20 #include <linux/sched/debug.h>
21 #include <linux/sched/task.h>
22 #include <linux/sched/task_stack.h>
23 #include <linux/seq_file.h>
24 #include <linux/tick.h>
25 #include <linux/threads.h>
26 #include <linux/resume_user_mode.h>
27 #include <asm/current.h>
28 #include <asm/mmu_context.h>
29 #include <linux/uaccess.h>
30 #include <as-layout.h>
31 #include <kern_util.h>
32 #include <os.h>
33 #include <skas.h>
34 #include <registers.h>
35 #include <linux/time-internal.h>
36 #include <linux/elfcore.h>
37 
38 /*
39  * This is a per-cpu array.  A processor only modifies its entry and it only
40  * cares about its entry, so it's OK if another processor is modifying its
41  * entry.
42  */
43 struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
44 
external_pid(void)45 static inline int external_pid(void)
46 {
47 	/* FIXME: Need to look up userspace_pid by cpu */
48 	return userspace_pid[0];
49 }
50 
pid_to_processor_id(int pid)51 int pid_to_processor_id(int pid)
52 {
53 	int i;
54 
55 	for (i = 0; i < ncpus; i++) {
56 		if (cpu_tasks[i].pid == pid)
57 			return i;
58 	}
59 	return -1;
60 }
61 
free_stack(unsigned long stack,int order)62 void free_stack(unsigned long stack, int order)
63 {
64 	free_pages(stack, order);
65 }
66 
alloc_stack(int order,int atomic)67 unsigned long alloc_stack(int order, int atomic)
68 {
69 	unsigned long page;
70 	gfp_t flags = GFP_KERNEL;
71 
72 	if (atomic)
73 		flags = GFP_ATOMIC;
74 	page = __get_free_pages(flags, order);
75 
76 	return page;
77 }
78 
set_current(struct task_struct * task)79 static inline void set_current(struct task_struct *task)
80 {
81 	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
82 		{ external_pid(), task });
83 }
84 
85 extern void arch_switch_to(struct task_struct *to);
86 
__switch_to(struct task_struct * from,struct task_struct * to)87 void *__switch_to(struct task_struct *from, struct task_struct *to)
88 {
89 	to->thread.prev_sched = from;
90 	set_current(to);
91 
92 	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
93 	arch_switch_to(current);
94 
95 	return current->thread.prev_sched;
96 }
97 
interrupt_end(void)98 void interrupt_end(void)
99 {
100 	struct pt_regs *regs = &current->thread.regs;
101 
102 	if (need_resched())
103 		schedule();
104 	if (test_thread_flag(TIF_SIGPENDING) ||
105 	    test_thread_flag(TIF_NOTIFY_SIGNAL))
106 		do_signal(regs);
107 	if (test_thread_flag(TIF_NOTIFY_RESUME))
108 		resume_user_mode_work(regs);
109 }
110 
get_current_pid(void)111 int get_current_pid(void)
112 {
113 	return task_pid_nr(current);
114 }
115 
116 /*
117  * This is called magically, by its address being stuffed in a jmp_buf
118  * and being longjmp-d to.
119  */
new_thread_handler(void)120 void new_thread_handler(void)
121 {
122 	int (*fn)(void *), n;
123 	void *arg;
124 
125 	if (current->thread.prev_sched != NULL)
126 		schedule_tail(current->thread.prev_sched);
127 	current->thread.prev_sched = NULL;
128 
129 	fn = current->thread.request.u.thread.proc;
130 	arg = current->thread.request.u.thread.arg;
131 
132 	/*
133 	 * callback returns only if the kernel thread execs a process
134 	 */
135 	n = fn(arg);
136 	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
137 }
138 
139 /* Called magically, see new_thread_handler above */
fork_handler(void)140 void fork_handler(void)
141 {
142 	force_flush_all();
143 
144 	schedule_tail(current->thread.prev_sched);
145 
146 	/*
147 	 * XXX: if interrupt_end() calls schedule, this call to
148 	 * arch_switch_to isn't needed. We could want to apply this to
149 	 * improve performance. -bb
150 	 */
151 	arch_switch_to(current);
152 
153 	current->thread.prev_sched = NULL;
154 
155 	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
156 }
157 
copy_thread(struct task_struct * p,const struct kernel_clone_args * args)158 int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
159 {
160 	unsigned long clone_flags = args->flags;
161 	unsigned long sp = args->stack;
162 	unsigned long tls = args->tls;
163 	void (*handler)(void);
164 	int ret = 0;
165 
166 	p->thread = (struct thread_struct) INIT_THREAD;
167 
168 	if (!args->fn) {
169 	  	memcpy(&p->thread.regs.regs, current_pt_regs(),
170 		       sizeof(p->thread.regs.regs));
171 		PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
172 		if (sp != 0)
173 			REGS_SP(p->thread.regs.regs.gp) = sp;
174 
175 		handler = fork_handler;
176 
177 		arch_copy_thread(&current->thread.arch, &p->thread.arch);
178 	} else {
179 		get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
180 		p->thread.request.u.thread.proc = args->fn;
181 		p->thread.request.u.thread.arg = args->fn_arg;
182 		handler = new_thread_handler;
183 	}
184 
185 	new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
186 
187 	if (!args->fn) {
188 		clear_flushed_tls(p);
189 
190 		/*
191 		 * Set a new TLS for the child thread?
192 		 */
193 		if (clone_flags & CLONE_SETTLS)
194 			ret = arch_set_tls(p, tls);
195 	}
196 
197 	return ret;
198 }
199 
initial_thread_cb(void (* proc)(void *),void * arg)200 void initial_thread_cb(void (*proc)(void *), void *arg)
201 {
202 	int save_kmalloc_ok = kmalloc_ok;
203 
204 	kmalloc_ok = 0;
205 	initial_thread_cb_skas(proc, arg);
206 	kmalloc_ok = save_kmalloc_ok;
207 }
208 
um_idle_sleep(void)209 void um_idle_sleep(void)
210 {
211 	if (time_travel_mode != TT_MODE_OFF)
212 		time_travel_sleep();
213 	else
214 		os_idle_sleep();
215 }
216 
arch_cpu_idle(void)217 void arch_cpu_idle(void)
218 {
219 	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
220 	um_idle_sleep();
221 }
222 
__uml_cant_sleep(void)223 int __uml_cant_sleep(void) {
224 	return in_atomic() || irqs_disabled() || in_interrupt();
225 	/* Is in_interrupt() really needed? */
226 }
227 
user_context(unsigned long sp)228 int user_context(unsigned long sp)
229 {
230 	unsigned long stack;
231 
232 	stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
233 	return stack != (unsigned long) current_thread_info();
234 }
235 
236 extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
237 
do_uml_exitcalls(void)238 void do_uml_exitcalls(void)
239 {
240 	exitcall_t *call;
241 
242 	call = &__uml_exitcall_end;
243 	while (--call >= &__uml_exitcall_begin)
244 		(*call)();
245 }
246 
uml_strdup(const char * string)247 char *uml_strdup(const char *string)
248 {
249 	return kstrdup(string, GFP_KERNEL);
250 }
251 EXPORT_SYMBOL(uml_strdup);
252 
copy_to_user_proc(void __user * to,void * from,int size)253 int copy_to_user_proc(void __user *to, void *from, int size)
254 {
255 	return copy_to_user(to, from, size);
256 }
257 
copy_from_user_proc(void * to,void __user * from,int size)258 int copy_from_user_proc(void *to, void __user *from, int size)
259 {
260 	return copy_from_user(to, from, size);
261 }
262 
clear_user_proc(void __user * buf,int size)263 int clear_user_proc(void __user *buf, int size)
264 {
265 	return clear_user(buf, size);
266 }
267 
268 static atomic_t using_sysemu = ATOMIC_INIT(0);
269 int sysemu_supported;
270 
set_using_sysemu(int value)271 void set_using_sysemu(int value)
272 {
273 	if (value > sysemu_supported)
274 		return;
275 	atomic_set(&using_sysemu, value);
276 }
277 
get_using_sysemu(void)278 int get_using_sysemu(void)
279 {
280 	return atomic_read(&using_sysemu);
281 }
282 
sysemu_proc_show(struct seq_file * m,void * v)283 static int sysemu_proc_show(struct seq_file *m, void *v)
284 {
285 	seq_printf(m, "%d\n", get_using_sysemu());
286 	return 0;
287 }
288 
sysemu_proc_open(struct inode * inode,struct file * file)289 static int sysemu_proc_open(struct inode *inode, struct file *file)
290 {
291 	return single_open(file, sysemu_proc_show, NULL);
292 }
293 
sysemu_proc_write(struct file * file,const char __user * buf,size_t count,loff_t * pos)294 static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
295 				 size_t count, loff_t *pos)
296 {
297 	char tmp[2];
298 
299 	if (copy_from_user(tmp, buf, 1))
300 		return -EFAULT;
301 
302 	if (tmp[0] >= '0' && tmp[0] <= '2')
303 		set_using_sysemu(tmp[0] - '0');
304 	/* We use the first char, but pretend to write everything */
305 	return count;
306 }
307 
308 static const struct proc_ops sysemu_proc_ops = {
309 	.proc_open	= sysemu_proc_open,
310 	.proc_read	= seq_read,
311 	.proc_lseek	= seq_lseek,
312 	.proc_release	= single_release,
313 	.proc_write	= sysemu_proc_write,
314 };
315 
make_proc_sysemu(void)316 int __init make_proc_sysemu(void)
317 {
318 	struct proc_dir_entry *ent;
319 	if (!sysemu_supported)
320 		return 0;
321 
322 	ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_ops);
323 
324 	if (ent == NULL)
325 	{
326 		printk(KERN_WARNING "Failed to register /proc/sysemu\n");
327 		return 0;
328 	}
329 
330 	return 0;
331 }
332 
333 late_initcall(make_proc_sysemu);
334 
singlestepping(void * t)335 int singlestepping(void * t)
336 {
337 	struct task_struct *task = t ? t : current;
338 
339 	if (!test_thread_flag(TIF_SINGLESTEP))
340 		return 0;
341 
342 	if (task->thread.singlestep_syscall)
343 		return 1;
344 
345 	return 2;
346 }
347 
348 /*
349  * Only x86 and x86_64 have an arch_align_stack().
350  * All other arches have "#define arch_align_stack(x) (x)"
351  * in their asm/exec.h
352  * As this is included in UML from asm-um/system-generic.h,
353  * we can use it to behave as the subarch does.
354  */
355 #ifndef arch_align_stack
arch_align_stack(unsigned long sp)356 unsigned long arch_align_stack(unsigned long sp)
357 {
358 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
359 		sp -= get_random_u32_below(8192);
360 	return sp & ~0xf;
361 }
362 #endif
363 
__get_wchan(struct task_struct * p)364 unsigned long __get_wchan(struct task_struct *p)
365 {
366 	unsigned long stack_page, sp, ip;
367 	bool seen_sched = 0;
368 
369 	stack_page = (unsigned long) task_stack_page(p);
370 	/* Bail if the process has no kernel stack for some reason */
371 	if (stack_page == 0)
372 		return 0;
373 
374 	sp = p->thread.switch_buf->JB_SP;
375 	/*
376 	 * Bail if the stack pointer is below the bottom of the kernel
377 	 * stack for some reason
378 	 */
379 	if (sp < stack_page)
380 		return 0;
381 
382 	while (sp < stack_page + THREAD_SIZE) {
383 		ip = *((unsigned long *) sp);
384 		if (in_sched_functions(ip))
385 			/* Ignore everything until we're above the scheduler */
386 			seen_sched = 1;
387 		else if (kernel_text_address(ip) && seen_sched)
388 			return ip;
389 
390 		sp += sizeof(unsigned long);
391 	}
392 
393 	return 0;
394 }
395 
elf_core_copy_task_fpregs(struct task_struct * t,elf_fpregset_t * fpu)396 int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
397 {
398 	int cpu = current_thread_info()->cpu;
399 
400 	return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
401 }
402 
403